The Effect of Multiple Member Failure on the Predicted Reliability of Fixed Jacket Structures

2008 ◽  
Author(s):  
D. Sanderson ◽  
A. Nelson ◽  
A. Stacey
Keyword(s):  
Ultimate Strength ◽  
Cross Correlation ◽  
Stress Redistribution ◽  
Design Strength ◽  
Inspection Interval ◽  
Jacket Structures ◽  
Effects Of Stress ◽  
Reliability Assessments ◽  
The Individual ◽  
Large Reserve

Current offshore inspection practice relies on the detection of gross damage, such as flooded member detection. Such an inspection philosophy relies upon the structure’s ability to withstand gross damage for an inspection interval based on the large reserve factors on the jacket design strength in both the undamaged and damaged conditions. This requires a demonstration of the structure’s strength in all of the possible damaged conditions with the most critical member removed. However, the load originally carried by the critical member is redistributed to other neighbouring members which must consequently have an impact on the design fatigue lives of other members and increase the probability of more members failing. Ignoring the effects of stress redistribution due to member failure could therefore result in under-prediction of the probability of a second member failing and hence an optimistic prediction of platform reliability. This paper aims to quantify the effects of stress redistribution on the prediction of platform reliability. Stress and ultimate strength analyses were performed on three platforms in 45m water depth with bracing configurations of varying structural redundancies, namely, single diagonal, inverted K and X-braced, to calculate the stress enhancement in all members due to the individual failure of all other members. These stress enhancements were input into probabilistic fracture mechanics models to calculate the increase in failure probability of these second members due to the failure of a first member. More than 1000 pushover analyses were performed to calculate the ultimate strength of the structures in all single-member failed conditions and many hundreds of dual member failed permutations for each jacket. A cross-correlation of the most significant stress redistribution results and pushover results was used to perform platform reliability assessments. The effect of including stress redistribution and dual member pushover results was shown to reduce the predicted platform reliability for all bracing configurations, mainly due to a number of dual-member failed conditions that weakened the jackets significantly. It is recommended that, in addition to performing single member failed pushover analyses, there is a need to assess dual-member failed conditions that drastically reduce platform strength.

The Impact of Stress Redistribution on Structural Reliability Predictions of Deepwater Jackets

2007 ◽  
Author(s):  
Ronald Schneider ◽  
David J. Sanderson ◽  
Simon D. Thurlbeck
Keyword(s):  
Best Practice ◽  
Structural Reliability ◽  
Stress Redistribution ◽  
Correction Factors ◽  
Structural Members ◽  
Jacket Structures ◽  
Effects Of Stress ◽  
Failure Conditions ◽  
The Impact ◽  
Water Depths

Structural reliability predictions for fixed jacket structures often involve calculating the probabilities of structural members failing and the overall collapse probabilities of the jackets existing in the corresponding damaged condition. It is current best practice to consider only single member failure conditions and to ignore multi member failure conditions since the probability of more than one member failing has been considered to be negligibly small. This approach assumes that the failure of a member is in no way related to the failure of another member, which implies that the two events are statistically independent. However, in reality the two events are not statistically independent since the failure of one member changes the stress state and therefore the failure probability of the remaining members. Two studies conducted to investigate the effects of stress redistribution on platform reliability predictions concluded that, by ignoring the effects of stress redistribution, platform reliability predictions could be significantly overestimated. However, they both concentrated on shallow water jackets and consequently a further study was performed to extend the existing work on stress redistribution to consider jacket structures in greater water depths. The study considered single and dual member failure conditions and compared the effects of including and excluding stress redistribution in reliability calculations. The findings of this work suggest that including stress redistribution reduces the predicted platform reliability. From the results, generic correction factors were derived for different inspection intervals, which account for stress redistribution and dual member failure. These correction factors can be applied to the probabilities derived using current best practice to determine a more realistic estimate of a structure’s reliability.

The Effects of Stress Redistribution Due to Member Failure on Structural Reliability of Offshore Steel Jackets

2002 ◽  
Author(s):  
A. Nelson ◽  
D. J. Sanderson ◽  
A. Stacey
Keyword(s):  
Structural Reliability ◽  
Structural Integrity ◽  
Stress Redistribution ◽  
Periodic Inspection ◽  
Inspection Interval ◽  
Time Period ◽  
Jacket Structures ◽  
Integrity Assurance ◽  
The Impact ◽  
Inspection Schedule

Current practice in providing structural integrity assurance of North Sea Steel Jacket structures relies upon periodic inspection of the sub-structures, with FMD being the preferred method of inspection. The time period between inspections, when employing FMD is dependent upon the structure’s level of redundancy. However, little, if any, consideration is given to the effect a failed member has on the stress distribution within the structure and the probability of a second member failing. A study has been completed that investigated the impact of stress redistribution following failure of a member. The study has considered the impact this has on fatigue lives of adjacent members/joints, and ultimately the impact on structural reliability. The findings from this study suggest that for the type of structures considered, the justification for a given inspection schedule should take due account of the impact of stress redistribution and the possibility that a structure might experience a second member failure during an inspection interval.

scholarly journals Insights to enhance the examination of tool marks in human cartilage

2021 ◽  
Author(s):  
Matthias Weber ◽  
Anja Niehoff ◽  
Markus A. Rothschild
Keyword(s):  
Light Microscope ◽  
Cross Correlation ◽  
Costal Cartilage ◽  
Correlation Coefficients ◽  
Human Cartilage ◽  
Cut Marks ◽  
Tool Marks ◽  
The Cross ◽  
Cleaning Methods ◽  
The Individual

AbstractThis work deals with the examination of tool marks in human cartilage. We compared the effectiveness of several cleaning methods on cut marks in porcine cartilage. The method cleaning by multiple casts achieved the significantly highest scores (P = 0.02). Furthermore, we examined the grain-like elevations (dots) located on casts of cut cartilage. The results of this study suggest that the casting material forms these dots when penetrating cartilage cavities, which are areas where the strong collagen fibres leave space for the chondrocytes. We performed fixation experiments to avoid this, without success. In addition, 31 casting materials were compared regarding contrast under light-microscope and 3D tool marks scanner. Under the light-microscope, brown materials achieved significantly higher values than grey (P = 0.02) or black (P = 0.00) whereas under the 3D scanner, black materials reached higher contrast values than grey (P = 0.04) or brown (P = 0.047). To compare the accuracy and reproducibility of 6 test materials for cartilage, we used 10 knives to create cut marks that were subsequently scanned. During the alignment of the individual signals of each mark, the cross-correlation coefficients (Xmax) and lags (LXmax) were calculated. The signals of the marks in agarose were aligned with significantly fewer lags and achieved significantly higher cross-correlation coefficients compared to all tested materials (both P = 0.00). Moreover, we determined the cross-correlation coefficients (XC) for known-matches (KM) per material. Agarose achieved significantly higher values than AccuTrans®, Clear Ballistics™, and gelatine (all P = 0.00). The results of this work provide valuable insights for the forensic investigation of marks in human costal cartilage.

scholarly journals Advancements of the examination of tool marks in human cartilage

2021 ◽  
Author(s):  
Matthias Weber ◽  
Anja Niehoff ◽  
Markus A. Rothschild
Keyword(s):  
Light Microscope ◽  
Cross Correlation ◽  
Costal Cartilage ◽  
Correlation Coefficients ◽  
Human Cartilage ◽  
Cut Marks ◽  
Tool Marks ◽  
The Cross ◽  
Cleaning Methods ◽  
The Individual

Abstract This work deals with the examination of tool marks in human cartilage. We compared the effectiveness of several cleaning methods on cut marks in porcine cartilage. The method cleaning by multiple casts achieved the significantly highest scores (P = 0.02). Furthermore, we examined the grain-like elevations (dots) located on casts of cut cartilage. The results of this study suggest that the casting material forms these dots when penetrating cartilage cavities, which are areas where the strong collagen fibers leave space for the chondrocytes. We performed fixation experiments to avoid this, without success. In addition, 31 casting materials were compared regarding contrast under light-microscope and 3D tool marks scanner. Under the light-microscope, brown materials achieved significantly higher values than grey (P = 0.02) or black (P = 0.00) whereas under the 3D scanner, black materials reached higher contrast values than grey (P = 0.04) or brown (P = 0.047). To compare the accuracy and reproducibility of 6 test materials for cartilage, we used 10 knives to create cut marks that were subsequently scanned. During the alignment of the individual signals of each mark, the cross-correlation coefficients (Xmax) and lags (LXmax) were calculated. The signals of the marks in agarose were aligned with significantly fewer lags and achieved significantly higher cross-correlation coefficients compared to all tested materials (both P = 0.00). Moreover, we determined the cross-correlation coefficients (XC) for known-matches (KM) per material. Agarose achieved significantly higher values than AccuTrans®, Clear Ballistics™, and gelatine (all P = 0.00). The results of this work provide valuable insights for the forensic investigation of marks in human costal cartilage.

Dynamic Behavior and Synchronization of an Automobile as a Complex System

2014 ◽  
Author(s):  
Claudia A. González-Cruz ◽  
Juan C. Jáuregui-Correa ◽  
Carlos S. López-Cajún ◽  
Mihir Sen
Keyword(s):  
Complex System ◽  
Wavelet Transforms ◽  
Cross Correlation ◽  
Correlation Coefficients ◽  
The Other ◽  
Accelerometer Data ◽  
Hilbert Transforms ◽  
The Road ◽  
The Individual ◽  
Analytical Tools

A complex system is composed of many interacting components, but the behavior of the system as a whole can be quite different from that of the individual components. An automobile is an example of a common mechanical system composed of a large number of individual components that are mechanically connected in some way and hence transmit vibrations to each other. This paper proposes a variety of inter-related analytical tools for the study of experimental data from such systems. In this work, experimental results of accelerometer data acquired at two locations in the automobile for two different kinds of tests are analyzed. One test is the response to impact on a stationary vehicle, and the other is the road-response to the vehicle being driven on a flat road at different speeds. Signals were processed via Fourier and wavelet transforms, cross-correlation coefficients were computed, and Hilbert transforms and Kuramoto order parameters were determined. A new parameter representing synchronization deficit is introduced. There is indeed some degree of synchronization that can be quantified between the accelerations measured at these two locations in the vehicle.

DECOMPOSITION OF OVERLAPPING PATTERNS BY CUMULATIVE LOCAL CROSS-CORRELATION

2006 ◽  
Vol 04 (02) ◽  
pp. 571-587
Author(s):  
SIMON B. KOGAN
Keyword(s):  
Cross Correlation ◽  
Repetitive Sequences ◽  
Software Implementation ◽  
Sequence Profile ◽  
Motif Position ◽  
Boundary Definition ◽  
Human Genomic ◽  
The Individual ◽  
Common Situation ◽  
Correlation Procedure

A large portion of the usual eukaryotic genome is comprised of repetitive sequences. A common situation, when several related but different repeat families share the same conserved motif, complicates repeat classification and repeat boundary definition. If the repeats are aligned by the motif position, then the sequence profile (pattern) resulting from the alignment will represent overlapping of the profiles (patterns) corresponding to the individual families. A novel algorithm for the decomposition of overlapping patterns is proposed. It can be used with both continuous and gapped patterns. The technique is based on accumulation of simultaneously occurring pattern features found by cross-correlation procedure with limited lag length; thus, the name is Cumulative Local Cross-Correlation (referred further as CLCC). Its sensitivity is tested on human genomic sequences. Software implementation of the algorithm is available on request from the author.

scholarly journals A Direct Link between Feature Tracking and Height Assignment of Operational EUMETSAT Atmospheric Motion Vectors

2014 ◽  
Vol 31 (1) ◽  
pp. 33-46 ◽  
Author(s):  
Régis Borde ◽  
Marie Doutriaux-Boucher ◽  
Greg Dew ◽  
Manuel Carranza
Keyword(s):  
Feature Tracking ◽  
Cross Correlation ◽  
Motion Vectors ◽  
Tracking Process ◽  
Extraction Scheme ◽  
Atmospheric Motion ◽  
Image Pixels ◽  
The Individual ◽  
Height Assignment ◽  
Atmospheric Motion Vectors

Abstract Height assignment (HA) is currently the most challenging task in the operational atmospheric motion vectors’ (AMV) extraction scheme. Several sources of error are associated with the height assignment step, including the sensitivity of the HA methods to several atmospheric parameters. However, one of the main difficulties is to identify, for the HA calculation, the most significant image pixels used in the feature-tracking process. The most widely used method selects the coldest pixels in a representative target box (e.g., coldest 25%) to infer the height of the detected feature, irrespective of what was tracked. This paper presents a method based on a closer link between the pixels used for tracking and their HA. The individual contribution to the overall tracking cross-correlation coefficient is used to identify the most significant pixels contributing to the tracking. This approach has been implemented operationally at European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) to derive AMVs since September 2012. This paper details the method, gives specific examples, and provides a first glance at its performances and benefits for the operational AMV production.

scholarly journals Reconstructing Surface Eruptive Sequence of 2018 Small Phreatic Eruption of Iwo-Yama Volcano, Kirishima Volcanic Complex, Japan by Infrasound Cross-correlation Analysis

2020 ◽  
Author(s):  
Dan Muramatsu ◽  
Takeshi Matsushima ◽  
Mie Ichihara
Keyword(s):  
Correlation Analysis ◽  
Cross Correlation ◽  
Phreatic Eruption ◽  
Volcanic Complex ◽  
Cross Correlation Analysis ◽  
Hazard Assessments ◽  
The Individual

Abstract The Iwo-yama volcano of the Kirishima Volcanic Complex in Japan had a small phreatic eruption in April 2018, which formed multiple vents. The activity was recorded by two infrasound sensors and two monitoring cameras which had been installed within 1 km of the vents. This study identified infrasonic signals from the multiple vents by a cross-correlation analysis between the two infrasound sensors. The analysis successfully revealed the signals from two main eruption craters and constrained the infrasound onsets at the individual vents in the two craters. We combined the results with the images from the cameras and reconstructed the sequence of the small phreatic eruption of Iwo-yama. Notably, the intense eruption accompanying remarkable infrasound delayed several hours to the eruption onset at each of the two craters. This study provides a sequence of the activities of the multiple vents in a phreatic eruption, which will be useful for understanding the phreatic eruption mechanism and hazard assessments.

Performance of Stabilized and Non-Stabilized PVA Nanofiber Textiles Subjected to Tension

2015 ◽  
Vol 732 ◽  
pp. 119-122 ◽  
Author(s):  
Zuzana Rácová ◽  
Zdeněk Prošek ◽  
Jaroslav Topič ◽  
Pavel Tesárek ◽  
Kateřina Indrová ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Ultimate Strength ◽  
Chemical Stability ◽  
Building Industry ◽  
Chemical Stabilization ◽  
Air Humidity ◽  
Physical Chemical ◽  
Moisture Barriers ◽  
The Individual ◽  
Strength And Ductility

Nanofiber textiles became indispensible in medicine and many other industries because of their unique properties. Recently, the pioneering works suggested their use also in a building industry in the form of moisture barriers. For a better chemical stability and resistance to air humidity it is suitable to stabilize the spun textiles. Our study is focused on the influence of the physical-chemical stabilization, also called crosslinking, on the mechanical properties of nanofiber textiles in tension, namely stiffness, strength and ductility. During the process of crosslinking the individual fibers bond in nodes, ensuring a better spatial integrity. However, the presented results indicate that the stabilized nanofiber textiles exhibit significantly lower ductility while their ultimate strength is lower only by about 10 %.

The Clinker Minerals Effect on the Cement Hardening Kinetic Constants

2019 ◽  
Vol 974 ◽  
pp. 217-223
Author(s):  
Shark M. Rakhimbaev ◽  
Tatiana V. Anikanova ◽  
Igor S. Rakhimbaev ◽  
Alexey S. Pogromsky
Keyword(s):  
Compressive Strength ◽  
Ultimate Strength ◽  
Sharp Decrease ◽  
Ultimate Compressive Strength ◽  
Kinetic Constants ◽  
The Individual ◽  
The Relationship ◽  
Positive Effect

The work is devoted to the study of the relationship between the individual clinker minerals content, the stone compressive strength in different periods of hardening and the binders kinetic hardening constants. It is shown that C3S and C2S affect the cements’ kinetic hardening constants in the early and long-term periods in different ways. There is a positive effect of C2S on the ultimate compressive strength and a sharp decrease in the dependence of the stone ultimate strength on C3S in the later periods. The initial hardening rate in high-cement cement is established to increase sharply with an increase in the C3A content from 5 to 12%. The increase in the C3A content up to 12% in low-cement cement has little effect on the initial hardening rate value.

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